The present invention relates to air conditioning systems and, more particularly, to Freon-type air conditioning systems where Freon is circulated by a compressor between an evaporator coil and a condenser coil wherein it is repetitively changed between liquid and gas states to effect cooling in the evaporator unit.
In mechanical air conditioning systems of the Freon-type, a compressor pumps heat-containing gaseous Freon to a condensing unit containing finned coils wherein cooling air is directed through the finned coils to cool the Freon to a liquid. Liquid Freon is then conducted to an evaporating unit also having finned coils therein wherein the liquid Freon is flashed to the gaseous state. The change of state from the liquid to gas phase is accompanied by a corresponding heat extraction from air being passed around the finned coils which cools the air for use in lowering the temperature of spaces to which it is then directed. The gaseous Freon is then returned to the compressor for recirculation.
To accomplish the cooling objectives in an optimum manner, the compressor, evaporator unit and condenser unit must be "sized" for operation together. Improper matching of volumes and flow rate capacities causes less than optimum performance. Most design parameters are established by the Air Conditioning and Refrigeration Institute (ARI). Thus, mechanical air conditioning systems of the type described above are designed to remove heat energy from a structure and discharge the heat into a design ambient condition of 95.degree. F., dry bulb. Unfortunately, as the ambient temperature increases, the cooling available to the structure may decrease by as much as 20%, while at the same time, the cooling requirement may increase by as much as 20%.
With the advent of recent recognitions of the shortage of available energy, the air conditioning industry has adopted Energy Efficiency Ratio (EER) as a tool to measure equipment performance in numerical quantities. The EER of a particular air conditioning system is obtained by dividing the cooling capacity in Btu's per hour (Btu/h) by power input in watts. Thus, as the ambient conditions increase above the design figure of 95.degree. F., the EER may decline by as much as 28%. This loss is a result of high compressor head pressures to obtain Freon condensation together with resulting high liquid temperatures. Moreover, power input may increase by as much as 13% as the head pressure rises and the cooling capacity is reduced by the amount of cooling required to cool the hot liquid to a cool liquid at the flash temperature in the evaporator.
Referring briefly to FIG. 1, a graph is shown displaying a number of critical factors. First, it can be seen that the typical cooling required of a structure increases beginning at early morning to a high in the early afternoon and then drops off until little or no cooling is required in the late evening. By comparison, the cooling available by dry bulb ambient air for cooling the condenser is higher in the cooler late and morning hours and becomes less as the ambient air heats during the hotter midday hours. As can be seen, typically the cooling required exceeds the cooling available during the hottest hours as indicated by the cross-hatched area of overlap between the cooling available and cooling required curves such that efficiency drops off and power consumption increases at precisely the time when optimum performance is needed most.
The reasons for these can be seen with reference to FIGS. 2, 3, and 4 wherein the performance of typical prior art mechanical air conditioners of the recirculating Freon-type employing dry bulb ambient air cooling are shown. In FIG. 2, it can be seen that as the ambient temperature increases above 95.degree. F., the structure cooling requirements continue to rise while the cooling available to the structure continues to decrease. Since the liquid leaving the condenser is at the ambient temperature, as shown in FIG. 3, the amount of heat absorption capability in the evaporator decreases correspondingly. This is shown graphically in FIG. 4.
Returning to FIG. 1, a third factor is graphed along with the two previously discussed. This factor is the cooling available from wet bulb temperature air. That is, air cooled by the evaporation of moisture therefrom in an adiabatic process at the indicated temperature. As can be seen, the cooling available is well above the graph of the cooling required and, in fact, increases during the hotter noon-day temperatures due to the lower moisture content of the ambient air.
By employing the potential available for cooling in wet bulb temperature air versus the normal use of dry bulb temperature air, it would appear that a more efficient air conditioner could be produced. This, in fact, has been tried with disasterous results. The obvious method is to direct the ambient air through a socall "swamp-cooler" to drop it to wet bulb temperature and then use that air to cool the condenser unit of a conventional Freon-type air conditioner. To do so, however, quickly results in the destruction of compressors improperly protected. In fact, many manufacturers of air conditioners specifically state in their sales materials that such operation of the unit voids the manufacturer's warranty on the product.
Wherefore, it is the object of the present invention to provide air conditioning apparatus of the recirculating Freon-type employing adiabatic cooling of the condenser as a part thereof so as to increase the cooling performance and boost the EER to levels previously unobtainable while, at the same time, eliminating the destructive effects previously encountered in such operation.